Novel heterozygous PLCG2 variant presenting with very early-onset perianal abscess

Case report Background: Mutations in the PLCG2 gene can cause PLCG2-associated antibody deficiency and immune dysregulation (PLAID) or auto-inflammation with PLCG2-associated antibody deficiency and immune dysregulation (APLAID). PLAID is characterized by urticarial eruptions triggered by evaporative cooling along with cutaneous granulomas. APLAID may present with early-onset skin inflammation and non-infectious granulomas, uveitis, and colitis. Method(s): Case report and literature review. We performed in silico analysis for variants of uncertain significance (VUS). Result(s): A 29-day-old boy presented to emergency department for failure to thrive. He was found to be SARS-CoV2 positive, had an E. coli UTI in the setting of bilateral perinephric masses which subsequently resolved. He also had a perianal soft tissue abscess measuring 4cm in diameter. Mom reported a similar infection when she was age 2. She also reported intermittent diffuse urticaria triggered following perspiration evaporation.Abscess wall histology showed diffuse neutrophil and lymphocytic infiltration, with cultures growing polymicrobial enteric flora. His serum immunoglobulins G, A, M, and E were within reference range. Naive and memory CD4, CD8, CD19 lymphocyte subsets (including NK cells) were also within age-appropriate reference range. He had a normal neutrophil oxidative burst measured using dihydrorhodamine (DHR) flow cytometry following PMA stimulation, which ruled out a diagnosis of chronic granulomatous disease. On evaporative cooling, the patient had a 2mm wheal with surrounding erythema which resolved rapidly with warming. A targeted primary immunodeficiency panel showed a heterozygous VUS in PLCG2, c.688C > G (p.Leu230Val). The variant was absent from major databases and had a calculated CADD score of 17.77. He had symptomatic resolution after completing 3 weeks of ceftriaxone and metronidazole antimicrobials. Given the concern for PLCG2-associated very early-onset inflammatory bowel disease (VEO-IBD), a fecal calprotectin was obtained at 3 months and found to be elevated (157 mcg/g [ < = 49 mcg/g]). However, he had no symptomatic or macroscopic evidence for VEO-IBD. Conclusion(s): Presence of very early onset abscesses has not been previously described in patients with heterozygous PLCG2 deficiency. This case adds to the expanding variable phenotype of PLCG-2-associated immune dysregulation.

Carriers of the p.P522R variant in PLCγ2 have a slightly more responsive immune system.

BACKGROUND: The rs72824905 single-nucleotide polymorphism in the PLCG2 gene, encoding the p.P522R residue change in Phospholipase C gamma 2 (PLCγ2), associates with protection against several dementia subtypes and with increased likelihood of longevity. Cell lines and animal models indicated that p.P522R is a functional hypermorph. We aimed to confirm this in human circulating peripheral immune cells. METHODS: We compared effects of p.P522R on immune system function between carriers and non-carriers (aged 59-103y), using in-depth immunophenotyping, functional B-cell and myeloid cell assays, and in vivo SARS-CoV-2 vaccination. RESULTS: In line with expectations, p.P522R impacts immune cell function only slightly, but it does so across a wide array of immune cell types. Upon B-cell stimulation, we observed increased PLCγ2 phosphorylation and calcium release, suggesting increased B-cell sensitivity upon antigen recognition. Further, p.P522R-carriers had higher numbers of CD20++CD21-CD24+ naive B cells and IgG1+ memory B cells. In myeloid cells, normalized ROS production was higher upon PLCγ2-dependent stimulation. On classical monocytes, CD33 levels were elevated. Furthermore, carriers expressed lower levels of allergy-related FcεRI on several immune cell subsets. Nevertheless, carriers and non-carriers had similar serological responses to SARS-CoV-2 vaccination. CONCLUSION: The immune system from p.P522R-carriers is slightly more responsive to stimulation than in non-carriers.

Successful retreatment of CLL with venetoclax following clonal evolution during 37 months of tirabrutinib and idelalisib

The BCL2-specific inhibitor, venetoclax, has demonstrated remarkable clinical activity in the treatment of chronic lymphocytic leukemia (CLL), either alone or in combination with CD20 antibodies. Nevertheless, patients who fail to attain a complete remission relapse, and require further therapy. Data on retreatment with venetoclax at disease progression are currently limited. Here, we report patterns of clonal evolution in an R/R CLL patient that has demonstrated successful retreatment. A 57 year-old lady with chemotherapy- refractory (FCR, RCHOP, high dose methyl prednisolone) TP53 mutant CLL was treated for 21 months with single-agent venetoclax in 2014 (NCT01889186). She attained an MRD positive CR with the resolution of massive lymphadenopathy and with only low-level (0.01%) disease in the bone marrow. However, she subsequently progressed rapidly with a lymphocyte doubling time of only 4 weeks and was treated with tirabrutinib and idelalisib in combination (NCT02968563) from December 2015 for 37 months before progressing December 2019. She was retreated with venetoclax and rituximab but died of COVID-19-induced respiratory failure in March 2020. To study the clonal evolution underlying these events, in vitro drug sensitivity assays and whole exome sequencing (WES) were used to study peripheral blood mononuclear (PBMC) and bone marrow samples. WES of sample 1 showed multiple mutations in CLL driver genes: SF3B1 R625C, KMT2C R4434Q, and TP53 R110L at VAFs of 37, 17, 35%, respectively. Mutations in other genes associated with CLL included FANCA L217F (47%) and SPEN P3402S (46%). At disease progression (sample 2), following venetoclax, there was the loss of detectable (WES at 100× coverage) TP53 R110L (with loss of 17p deletion on interphase FISH and analysis of copy number) but maintenance of SF3B1 R625C (44%), KMT2C R4434Q 30%), FANCA L217F (47%), and SPEN P3402S (55%). These data, therefore, suggest the TP53 mutant subclone was largely lost during therapy. No other mutations were identified as possible resistance mediators. There were no detectable BCL2 mutations. In vitro drug sensitivity testing to venetoclax showed an EC50 of 228nM (CLL EC50 usually 3-5 nM). The patient was then treated with the BTK inhibitor tirabrutinib in combination with idelalisib, with an excellent clinical response. After 10 months (sample 3, during the lymphocytosis induced by BTKi/PI3Kdi) SF3B1, KMT2C, FANCA, and SPEN mutations were detected at VAFs of 26, 30, 54, and 56%, respectively. At this point the TP53 R110L mutation was detected again at a VAF of 4%, indicating that stopping venetoclax allowed the clone to re-emerge. At this time, there were no detectable BTK or PLCG2 mutations. The patient then responded for a further 37 months before disease progression. At progression (sample 4), SF3B1, KMT2C, FANCA, and SPEN mutations were still detected in the peripheral blood at VAFs of 43, 31, 48, and 50%, respectively. The VAF of the TP53 R110L mutation had increased to 33%. Additionally, a BTK mutation (T474I) was identified with a VAF of 16%. Identical results were obtained using a bone marrow sample. Now, however, in vitro analysis demonstrated a high degree of sensitivity to venetoclax (EC50 0.72 nM). The patient was, therefore, retreated with venetoclax and rituximab. At the point of re-treatment, VAFs were maintained, with the emergence of a new subclonal NOTCH1 G1001D mutation at a VAF of 3%. The patient, unfortunately, died 4 months after commencing therapy due to COVID-19 associated pneumonitis. A full disease reassessment was not made but the patient's blood count had normalized, with rapid clearance of CLL cells from the peripheral blood, recovery of normal hematological indices, resolution of splenomegaly, and partial resolution of lymphadenopathy on CT scan. These data, therefore, suggest that re-treatment with venetoclax in CLL can be successful. Regaining sensitivity to venetoclax may largely depend on shifting clonal dynamics. The molecular basis of venetoclax resistance in this case is currently being investigated. A so in this particular case, it appears that the TP53 mutant subclone was more sensitive to BCL2 inhibition than TP53 wild-type subclone(s), and was largely eliminated by initial venetoclax treatment, contrasting with recently published data suggesting resistance of TP53 mutant hematological malignancies to BCL2 inhibition due to increased thresholds for BAX/BAK activation (Thijssen et al., 2021).

Combined Ibrutinib and Venetoclax for First-Line Treatment of Patients with Chronic Lymphocytic Leukemia (CLL): Focus on Long-Term MRD Results

Background: Ibrutinib (IBR) and venetoclax (VEN) combination is a highly effective therapy for patients (pts) with CLL (Jain, NEJM 2019;Wierda, ASH 2020;Kater, EHA 2021). We previously reported results of the first-line cohort of a phase II trial of combined IBR and VEN for high-risk pts with CLL (Jain, NEJM 2019;Jain, JAMA Oncology 2021). Here we report updated data for these pts with focus on MRD. Methods: Pts with previously untreated CLL meeting IWCLL treatment criteria were enrolled. All pts had at least one high-risk feature: del(17p), mutated TP53, del(11q), unmutated IGHV, or age ≥65 years (yrs). Pts received IBR 420 mg daily for 3 cycles followed by addition of VEN (weekly dose-escalation to 400mg daily). Combined therapy was given for 24 cycles (28 days/cycle). Pts with bone marrow (BM) undetectable MRD (U-MRD) (flow cytometry;sensitivity 10 -4) at 24 cycles of combined therapy discontinued both VEN and IBR;MRD+ pts continued IBR. A trial amendment allowed an additional 12 cycles of combined VEN and ibrutinib for pts who remained BM MRD+ after Cycle 24. Response assessments were performed using BM and CT imaging studies (2008 IWCLL criteria). U-MRD was defined as <0.01%;low MRD+ 0.01% to <1%;high MRD+ ≥1%. Progression-free survival (PFS) was assessed as the time from the start of study drug to CLL progression, Richter transformation, or death from any cause. Blood MRD was monitored every 6 months in pts off treatment or on ibrutinib monotherapy beyond 24 cycles of combined treatment. Results: A total of 80 pts were enrolled. Baseline characteristics are shown in Table 1. The median follow-up was 44.1 months. Five pts came off study during 1 st 3 cycles of IBR monotherapy;75 pts initiated VEN. We previously reported that after 12 cycles of the combination, 45/80 (56%) achieved BM U-MRD remission;24/80 (30%) were BM MRD-positive (low MRD+, n=19;high MRD+, n=5). After 24 cycles of the combination, 53/80 (66%) achieved BM U-MRD remission;14/80 (17%) were BM MRD+ (low MRD+, n=13;high MRD+, n=1). Overall, 60/80 (75%) achieved BM U-MRD as the best response. Updated PFS is provided in Figure 1. Of the 53 pts who were BM U-MRD at the end of cycle 24 of the combination, 52 pts had a subsequent blood MRD assessment done in follow-up (1 missed due to COVID-19);51/53 discontinued all therapy, 2 pts continued IBR per treatment physician discretion. With a median time of 18.4 months post Cycle 24, 8 pts had recurrence of blood MRD (defined as MRD ≥ 0.01% in 2 consecutive visits) in follow-up with 1 pt with CLL progression. The sole pt with CLL progression had mutated IGHV with del(11q) and NOTCH1 mutation. The pt had delayed achievement of BM U-MRD with the pt achieving U-MRD for the first time at the end of Cycle 24 of combined therapy. She was noted to have disease progression 22 months off therapy;BTK or PLCG2 mutation were not detected and the patient is currently in clinical remission on acalabrutinib. The time to MRD conversion for these 53 pts is shown in Figure 2. There were 14 pts who were BM MRD+ at the end of cycle 24 of the combination (low MRD+, n=13;high MRD+, n=1). The only pt with high-MRD+ at end of cycle 24 was noted to have Richter transformation at that time. The remaining 13 pts (all low MRD+ in BM, range 0.01-0.56%) continued IBR monotherapy. With a recent trial amendment, MRD+ pts after Cycle 24 could get 12 additional cycles of venetoclax;9/13 pts have resumed VEN. 6/9 pts have achieved U-MRD remission. 2 pts had Richter transformation and 3 pts have died (Jain, JAMA Oncology 2021). Conclusions: We report long term follow-up of combined IBR and VEN in first-line CLL. Remissions were durable with some pts having recurrence of blood MRD in follow-up, which may be an early indicator of relapse. In a small subset of the pts with BM MRD+ disease at 24 cycles of combined therapy, additional VEN appears to lead to U-MRD remission in majority of the pts. Whether this will lead to improved long-term PFS remains to be determined. [Formula presented] Disclosures: Jain: TG Therapeutics: Honoraria;Beigene: Honoraria;Janssen: Honoraria;Fate Therapeutics: Research Funding;Aprea Therapeutics: Research Funding;Precision Biosciences: Honoraria, Research Funding;Incyte: Research Funding;Adaptive Biotechnologies: Honoraria, Research Funding;Cellectis: Honoraria, Research Funding;ADC Therapeutics: Honoraria, Research Funding;Servier: Honoraria, Research Funding;Pfizer: Research Funding;Bristol Myers Squibb: Honoraria, Research Funding;AstraZeneca: Honoraria, Research Funding;Genentech: Honoraria, Research Funding;AbbVie: Honoraria, Research Funding;Pharmacyclics: Research Funding. Thompson: AbbVie: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding;Amgen: Other: Institution: Honoraria, Research Grant/Funding;Genentech: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding;Adaptive Biotechnologies: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding, Expert Testimony;Pharmacyclics: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding;Janssen: Consultancy, Honoraria;Gilead: Other: Institution: Advisory/Consultancy, Honoraria. Ferrajoli: BeiGene: Other: Advisory Board, Research Funding;Janssen: Other: Advisory Board;AstraZeneca: Other: Advisory Board, Research Funding. Burger: Novartis: Other: Travel/Accommodations/Expenses, Speakers Bureau;TG Therapeutics: Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau;Janssen: Consultancy, Other: Travel/Accommodations/Expenses, Speakers Bureau;Beigene: Research Funding, Speakers Bureau;Pharmacyclics LLC: Consultancy, Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau;Gilead: Consultancy, Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau;AstraZeneca: Consultancy. Borthakur: GSK: Consultancy;ArgenX: Membership on an entity's Board of Directors or advisory committees;University of Texas MD Anderson Cancer Center: Current Employment;Protagonist: Consultancy;Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees;Astex: Research Funding;Ryvu: Research Funding;Takeda: Membership on an entity's Board of Directors or advisory committees. Takahashi: Symbio Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy;Celgene/BMS: Consultancy;GSK: Consultancy. Sasaki: Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees;Pfizer: Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy, Research Funding. Kadia: Cellonkos: Other;Aglos: Consultancy;Dalichi Sankyo: Consultancy;AbbVie: Consultancy, Other: Grant/research support;BMS: Other: Grant/research support;Amgen: Other: Grant/research support;Cure: Speakers Bureau;Jazz: Consultancy;Genentech: Consultancy, Other: Grant/research support;Liberum: Consultancy;Novartis: Consultancy;Pfizer: Consultancy, Other;Pulmotech: Other;Sanofi-Aventis: Consultancy;AstraZeneca: Other;Astellas: Other;Genfleet: Other;Ascentage: Other. Konopleva: Sanofi: Other: grant support, Research Funding;Cellectis: Other: grant support;Calithera: Other: grant support, Research Funding;KisoJi: Research Funding;Agios: Other: grant support, Research Funding;Ascentage: Other: grant support, Research Funding;AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding;Ablynx: Other: grant support, Research Funding;Stemline Therapeutics: Research Funding;Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding;AstraZeneca: Other: grant support, Research Funding;Rafael Pharmaceuticals: Other: grant support, Research Funding;Genentech: Consultancy, Honoraria, Other: grant support, Research Funding;F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support;Forty Seven: Other: grant support, Research Funding;Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights;Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights. Alvarado: BerGenBio: Research Funding;Jazz Pharmaceuticals: Research Funding;Astex Pharmaceuticals: Research Funding;Sun Pharma: Consultancy, Research Funding;MEI Pharma: Research Funding;FibroGen: Research Funding;Daiichi-Sankyo: Research Funding;CytomX Therapeutics: Consultancy. Yilmaz: Pfizer: Research Funding;Daiichi-Sankyo: Research Funding. DiNardo: Notable Labs: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees;Novartis: Honoraria;Takeda: Honoraria;Celgene, a Bristol Myers Squibb company: Honoraria, Research Funding;Forma: Honoraria, Research Funding;AbbVie: Consultancy, Research Funding;GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees;Bristol Myers Squibb: Honoraria, Research Funding;ImmuneOnc: Honoraria, Research Funding;Agios/Servier: Consultancy, Honoraria, Research Funding;Foghorn: Honoraria, Research Funding. Bose: Kartos Therapeutics: Honoraria, Research Funding;Sierra Oncology: Honoraria;Novartis: Honoraria;Constellation Pharmaceuticals: Research Funding;NS Pharma: Research Funding;Celgene Corporation: Honoraria, Research Funding;Blueprint Medicines: Honoraria, Research Funding;Pfizer: Research Funding;Promedior: Research Funding;Astellas: Research Funding;Incyte Corporation: Honoraria, Research Funding;BMS: Honoraria, Research Funding;CTI BioPharma: Honoraria, Research Funding. Pemmaraju: Blueprint Medicines: Consultancy;LFB Biotechnologies: Consultancy;Novartis Pharmaceuticals: Consultancy, Other: Research Support, Research Funding;ASCO Leukemia Advisory Panel: Membership on an entity's Board of Directors or advisory committees;Dan's House of Hope: Membership on an entity's Board of Directors or advisorycommittees;Roche Diagnostics: Consultancy;MustangBio: Consultancy, Other;Affymetrix: Consultancy, Research Funding;Samus: Other, Research Funding;ImmunoGen, Inc: Consultancy;ASH Communications Committee: Membership on an entity's Board of Directors or advisory committees;Aptitude Health: Consultancy;Plexxicon: Other, Research Funding;Springer Science + Business Media: Other;Protagonist Therapeutics, Inc.: Consultancy;HemOnc Times/Oncology Times: Membership on an entity's Board of Directors or advisory committees;Clearview Healthcare Partners: Consultancy;Abbvie Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding;CareDx, Inc.: Consultancy;Sager Strong Foundation: Other;Daiichi Sankyo, Inc.: Other, Research Funding;Incyte: Consultancy;Stemline Therapeutics, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding;Bristol-Myers Squibb Co.: Consultancy;DAVA Oncology: Consultancy;Pacylex Pharmaceuticals: Consultancy;Celgene Corporation: Consultancy;Cellectis S.A. ADR: Other, Research Funding. Jabbour: Amgen, AbbVie, Spectrum, BMS, Takeda, Pfizer, Adaptive, Genentech: Research Funding. Wang: Stemline Therapeutics: Honoraria. Kantarjian: Taiho Pharmaceutical Canada: Honoraria;Precision Biosciences: Honoraria;Immunogen: Research Funding;Daiichi-Sankyo: Research Funding;Jazz: Research Funding;BMS: Research Funding;AbbVie: Honoraria, Research Funding;Pfizer: Honoraria, Research Funding;Novartis: Honoraria, Research Funding;NOVA Research: Honoraria;KAHR Medical Ltd: Honoraria;Ipsen Pharmaceuticals: Honoraria;Astra Zeneca: Honoraria;Astellas Health: Honoraria;Aptitude Health: Honoraria;Amgen: Honoraria, Research Funding;Ascentage: Research Funding. Wierda: Juno Therapeutics: Research Funding;AstraZeneca: Research Funding;Xencor: Research Funding;Janssen: Research Funding;Loxo Oncology, Inc.: Research Funding;Cyclacel: Research Funding;Oncternal Therapeutics, Inc.: Research Funding;Miragen: Research Funding;KITE Pharma: Research Funding;Sunesis: Research Funding;Gilead Sciences: Research Funding;Acerta Pharma Inc.: Rese rch Funding;Pharmacyclics LLC, an AbbVie Company: Research Funding;Karyopharm: Research Funding;Genentech: Research Funding;GSK/Novartis: Research Funding;Genzyme Corporation: Consultancy;AbbVie: Research Funding. OffLabel Disclosure: The combination of ibrutinib and venetoclax is not FDA approved